Devices, systems, and methods for accurately measuring blood pressure are disclosed and, more specifically, devices, systems, and methods that use inclination from a vertical or substantially vertical orientation to properly position the blood pressure monitor with respect to the subject's myocardium and to determine, inter alia, to which wrist the blood pressure monitor is attached.
Non-invasive, oscillometric blood pressure monitors (BPMs) are adapted to sense pulsewaves generated by the beating of the myocardium and the blood flow of a mammalian subject, precluding the need for more-subjective, auscultatory methods that require use of a stethoscope and/or of a human ear. Conventionally, BPMs include a pressure-applying device, e.g., a cuff, a sensing device, and a processing device. The cuff is applied to an external surface—usually an appendage, extremity or digit—of the mammalian subject. Then a controllable pressure is applied through the cuff to the external surface until the mammalian subject's local artery is occluded.
Once the local artery has been occluded, the sensing device detects and, in some instances, records pulsewave data corresponding to movement of the mammalian subject's myocardium and/or the pulsing of blood through the mammalian subject's arteries. The sensing device generates pulsewave data, which it transmits to the processing device. From pulsewave data, the processing device calculates pressure data, from which the maximum arterial pressure (systolic) and minimum arterial pressure (diastolic) are determined.
Conventionally, a blood pressure monitor (BPM) is affixed to some portion of a mammalian body part, e.g., a finger tip, wrist, upper arm, and the like, which is further positioned at or substantially at the same or substantially the same elevation as the mammalian subject's myocardium. Error results whenever the myocardium and BPM are not positioned at the same elevation. Indeed, if the BPM is located below the myocardium, measured or estimated blood pressure levels will be slightly higher than true, while if the BPM is located above the myocardium, pressure levels will be slightly lower than true.
The prior art includes electronic BPMs having a posture detector that is adapted to evaluate a relationship between the inclination of the electronic BPM with respect to a horizontal surface. These devices are designed to maintain the electronic BPM between an upper inclination limit (b) and lower inclination limit (a), which is approximately at or substantially at the same elevation as the myocardium.
This approach, however, introduces further measurement error when the subject has an abnormal size (height or relative body dimensions) that might cause the mammalian subject's myocardium not to be at the same elevation as the electronic BPM. Moreover, this approach typically only measures a pitch angle, further assuming that the forearm distance between the elbow resting on the horizontal place and the BPM located at the subject's wrist is the same for all subjects.
Conventional BPMs also suffer from a lack of “ambidexterity”, which is to say that the devices include one program for when the BPM is affixed to the left wrist and a second program for when the BPM is affixed to the right wrist. Failure to use the BPM on the correct extremity or incorrectly inputting the correct extremity of application, may result in inaccurate blood pressure measurements.
Accordingly, it would be desirable to provide a BPM that takes into account a roll angle, to provide better accuracy by detecting the proper position of the BPM. It would also be desirable to provide a BPM that is “ambidextrous”, which is to say that, the BPM is able to determine internally to which wrist the device is attached without requiring user input.